London ? British troops in Iraq have an important job to do and there is no fixed timetable for their withdrawal, Prime Minister Gordon Brown said Monday, despite speculation that Britain will soon announce a major pullout.

Brown has said a decision on the future of the 5,500 British troops in Iraq could be announced when Parliament returns from its summer break in October. But in a letter to Liberal Democrat leader Menzies Campbell, Brown rejected the opposition party’s demand to rethink the Iraq strategy.

“As I have made clear, decisions on U.K. force levels and posture in Iraq are dictated by conditions on the ground,” Brown wrote in the letter, which was released by his office.

Brown said Britain would “fulfill our obligations to the government and people of Iraq and the United Nations.” He rejected calls for “a predetermined exit timetable that would undermine our international obligations, as well as hindering the task of our armed forces and increasing the risks they face.”